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Discussion on error types

Contents (click to jump to a section)

• Summary announcement
• The seminar / discussion
  • A proposed framework for errors
  • Causation and accident analysis

Summary announcement

I will propose briefly what seems to me a new idea, then invite the audience to discuss it, particularly by offering cases that either fit or undermine the proposed idea(s). As many of the audience will know the field better than I do, this is crucial. In fact I have 2 such topics, but will only get to the second one, if there is little discussion of the first.

The first idea is to apply the 3 way classification of individual errors into slips, rule-based mistakes, and knowledge-level mistakes to 4 levels: the individual, the team or group, the organisation, and society. Management errors can perhaps be understood as appearing in several places in this 12-type scheme.

The seminar / discussion

The talk is to GIST at 4pm Thur 13th April 2000, room F121, Computing Science.

A proposed framework for errors

A 4-way classification of individual human error is now widely used:

• Slips: Actual behaviour fails to conform to the intention/plan (wrong action).
• Lapses: Actual behaviour fails to conform to the intention/plan (omitted action, memory failure).
• Rule-based mistake: wrong rule selected for action i.e. behaviour conforms to immediate intention, but intention, while consistent with a viable rule for action, is inconsistent in this case with wider knowledge.
• Knowledge-based mistake: error in generating a novel plan for a novel situation.

My proposal is to apply (cross, multiply) this 4-way classification with 4 levels:

• The individual. As above. This is in effect analysing the interaction (and inconsistencies) of parts or aspects of a person's mind with each other.
• The team or group. Group error. I.e. problems arising essentially from the interaction of individuals.
• The organisation. Problems arising from the interaction of parts of the organisation, and perhaps more importantly, from different goals and policies within an organisation.
• Society as a whole. Here, we can analyse shortcomings of the configurations of institutions and organisations in our society: do we have a wholly useful accident analysis procedure? Is government playing too much, too little, the wrong role? etc. Are legal procedures in fact making things less safe by obstructing the free cooperation that is important to understanding what went wrong?

A link.

Notes:

• By "team" I'm thinking of a small group e.g. of 6 people who interact personally even if they never meet face to face (e.g. pilot and air traffic controller, train driver and signalman);
• while by "organisation" I'm thinking of big entities like Railtrack or an airline, not small companies that operate as a team.
• Should there be a further "top" level of error due to ignorance? Certainly, not knowing something leads to mistakes. But we not feel that is an error, as in general that would imply a norm of omniscience. On the other hand, ignorance is often regarded as culpable (e.g. in law). A car driver drives into you, not through malice, but because they weren't looking. And many/most errors by physicians (as opposed to surgeons and nurses) are due to not getting the right information, rather than drawing the wrong conclusion from the available information. This could be seen as culpable due to the omitted information-getting action, thus making it an error after all.
• One can talk of management of oneself, one's time, a team, or an organisation. Thus "management errors" can appear at several levels here. Of interest here is the possibility of understanding something about management errors as conflicts between different aspects of knowledge and intentions, analogous to individual errors, at higher levels. For instance, rule-based mistakes at the organisational level might be cases where the wrong rule or SOP is acted on; while knowledge-based errors correspond to policy errors: where senior management think out and enact a policy that turns out not to further the company's interests taken as a whole.

• A number of errors seem to derive from the faulty equating (i.e. conflation) of two things in a person's mind; but this cuts across categories. E.g. slips where you press an adjacent key to the proper one; capture errors of the kind where you assimilate the wrong object to a rule e.g. putting the salad in the oven; Abermule where both stationmaster and driver take the token but don't check if it is the right one; Welwyn, where the signalman seems to have done one or both of: sent 'train out of section' on wrong instrument (and so referring to wrong line), or confounded the first and second express so that he attributed his memory of the first passing to the second.
• Slip and mistakes: is this basic distinction in fact clear and tenable? I've always had intermittent trouble with this. In both cases there is a real sense in which the person has a goal/intention, which is incorrectly developed (otherwise we and he couldn't recognise it later as an error i.e. a contraction between what he wanted/wished/meant to do and what he did do). In any simple program, or model of the mind as software, there is no particular line just a big hierarchy of goals being subdivided into subgoals. In both cases, the low level actions don't properly match the high level goals they were meant to accomplish. How can you draw a line? One attempt would be pre-stored plans vs. new ones (mistakes are errors in calculating new plans; slips in executing old ones). Another is basically relative to consciousness: in slips the person is at no time aware of a wrong intention, but in mistakes they are.
• There is a distinction in Organisational Psychology (and perhaps management studies) between 3 ways individuals interact, and hence ways in which individuals my be organised:
  • Clan: individuals take on the goals of the leader, as opposed to plans, rules, or anything else. They do what she or he says and/or wants. They act to please the person, taking all their interests into account.
  • Bureaucracy: individuals follow the ordained rules. This means they don't do what the head says on a whim, but equally, they are liable to follow the rules even in cases where the outcome clearly conflicts with the apparent goal (reason for) the rules.
  • Market: individuals take no account whatsoever of the others' interests, but negotiate each action (purchase) separately, on the basis of it being in both the party's interest on this occasion.
  
  This of course may be illuminating to bear in mind in considering how things can go wrong both in teams and organisations (and societies as a whole). (This distinction maps, apparently, on to the distinction in an individual's mind between goal, plan of action for that goal, and single executed actions.)

Causation and accident analysis

• Causes have no part in pure science (which describes relationships), only in engineering. Causes are inherently relative to human capacity for action and hence intentions and wishes, not to facts about the world.
• All events have multiple (actually, infinite) causes. Talking about "the cause" is a childish, and sometimes dangerous, logical error.
• We select out from this infinite set only those causes we think we can and want to change.
• In analysing the cause of an accident, we compare what happened against norms, selecting out deviations from these expectations. "Human error" refers to when a person acts against what was expected of them; "act of god" refers to a natural process that went against expectation.
• Recommendations, however, are about changing what is done. These again must be selected for what can be done; and in fact, for what can be afforded. It follows that accident reports can only be sensibly written by those with an equal knowledge of safety issues and industry costs.

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